The present invention relates to optical bar code scanners and more specifically to a bar code scanner diagnostic method.
Optical scanners are well known for their usefulness in retail checkout and inventory control. Optical scanners generally employ a laser diode, the light from which is focused and collimated to produce a scanning beam. A motor-driven mirrored spinner directs the beam against a plurality of stationary mirrors, and directs the reflected light from the bar code label to a detector. The pattern produced by such a scanner is characterized by lines oriented at various angles to one another.
During manufacturing, a scanner is tested to ensure that it shuts off when power is removed and turns on when power is applied. Scanner performance data is typically not taken during manufacturing and, therefore, is not available for comparison and analysis when the scanner fails in the field.
Routine scanner diagnostic tests are implemented during each application of power to the scanner and during each attempted scan of a bar code label. The power-on diagnostic check tests the firmware and determines whether power is available to the motor and laser. The check during each scan is a check performed by the scanner operator who merely determines whether the scanner was able to read a bar code label based upon a visual or aural indication.
After a scanner failure, a common diagnostic test of the scanner after a scanner failure includes the steps of positioning a tag having a bar code label printed thereon over a scan line and providing audible feedback to the diagnostic technician if the tag is successfully read. Such a test is imprecise and the results are open to subjective judgment. It cannot be reliably used to diagnose problems in which the power-on diagnostic program reports a "no-fault" operation condition or intermittent problems caused by tolerance errors, failing parts, or the scanning environment.
Therefore, it would be desirable to provide a reliable bar code scanner diagnostic method, especially for diagnosing scanner failures in the field.